Step 1Heat the broiler. Cut the bread into large chunks. Cut off the bottom crust and most of the top and side crusts. Brush the bread with 3 tablespoons olive oil. Broil briefly to crisp and lightly color the surface. Turn the bread chunks over and crisp the other side. Trim any charred tips and tear the chunks into irregular pieces, a combination of: 2-inch pieces, some that are bite-sized and some that are no more than fat crumbs. You should have about 12 cups.
Step 2Combine 1 cup olive oil with the Champagne vinegar, 1 teaspoon salt and one-eighth teaspoon pepper. Toss about three-fourths of this vinaigrette with the torn bread in a wide bowl (reserve the remaining vinaigrette). The bread will be unevenly dressed. Taste one of the more saturated pieces and if it is bland, season to taste with a little more salt and pepper and toss again.
Step 3Place the cranberries in a bowl and moisten them with the red wine vinegar and warm water and set aside.
Step 4While the turkey is roasting, place the pecans in a small baking pan and set them in the oven to warm through. Add them to the bread.
Step 5Place 1 tablespoon olive oil in a small skillet; add the garlic and scallions and cook over medium-low heat, stirring constantly, until softened, about 3 minutes. Don't let them color. Scrape these into the bread and fold to combine.
Step 6Drain and fold in the cranberries. Dribble the turkey stock or lightly salted water over all and fold again. Taste a few pieces of the bread, a fairly saturated one and a dryish one. If either is bland, season to taste with salt, pepper or a few drops of vinegar, then toss well again.
Step 7Pile the bread salad in a large baking dish and tent it very loosely with aluminum foil. Place it in the 350-degree oven when you remove the roasted turkey to rest. Turn off the oven and leave it in for 20 to 30 minutes. Set a wide salad bowl in a warm spot. Remove the salad greens from the refrigerator so they will be at room temperature when you add them to the bread salad.
Step 8Just after you carve the turkey, tip the bread salad into the wide salad bowl. It will be steamy hot; a mixture of soft, moist wads, crispy-on-the-outside-but-moist-in-the-middle wads, and a few downright crispy ones. Add the greens, a drizzle of the reserved vinaigrette and fold. Taste again before serving and adjust seasoning.